My recent forays into freezer-bag cooking have yielded mixed results.

This summer in the ADK's it worked great for two of us. I made a double-thickness fleece cozy and boiled water with a Caldera Cone. Temperatures never went below 50 F.

Last week at the Grand Canyon things did not go so well. Temperatures were usually in the mid-30's at dinner time. I used a cozy made out of 1.1 oz nylon and 5 oz Climashield, about the same thickness as the fleece cozy but one half the weight.

The problem was that although the food rehydrated, by the time it was ready, 5 mins or sometimes a few mins more, it was only luke-warm.

I first thought the cozy was too thin, but then I noticed that just after pouring (say) 2 cups of boiling water into the bag, it was already sort of cool. That is, the ingredients were cold enough that much of the heat from the hot water was lost right at the start.

This was especially true if one of the ingredients was something that had been rehydrating all day long, e.g something that had 3/4 cup of cold water already in it.

How do you avoid such problems? Was my cozy not good enough? Or is there a lower temperature limit to freezer-bag cooking.

I've done fbc down to 30 with no problem but it was all dry. If I was to start with cold water in the bag I would use the one pot method meaning to put everything in the pot then boil and put into a pot cozy. I made one out of aluminum-bubble wrap, works great!!

It's the cold water already in the bag that's the problem. You have to use 100% boiling water - or cook in the pot.

Cheers

Two things:

One is a thicker cozy with a wind shedding cover. Doesn't mean heavy nor thick either.

Second is time. If properly insulated your meal will stay warm for 30 or more minutes - even in freezing temps.

Bonus: Put your bag into the cozy BEFORE you add the water. This slows down loss of heat as you pour in the water. Water does not have to be boiling either - a few degrees below is just fine -if your cozy is correct :-)

As for items that were already hydrated in cool water, that water WILL lower your boiling water quite fast. Most items only need warm water and 5 to 10 minutes to rehydrate (15 at most) so honestly? Rehydrate those items right before eating.

For pre-rehydrating I've found that you just need to get the process started a tiny bit. A couple tablespoons of water added in the morning seems to work best. Too much too soon and stuff turns to mush.

The biggest rehydrating time-consumer has always been chunks of dried meat. We keep them separate and only add water to the meat. Then mix all ingredients when you add the hot water.

Sarah says "near boiling" but remember that fully boiling water high in the mountains is 20F cooler than at sea level.

"At high altitudes, the atmospheric pressure is less and the boiling point of the liquid will reached at a lower temperature. To check the temperature of the boiling point of water in your altitude, place a thermometer in boiling water (suspend it in the water so that it does not touch the pan bottom). Leave the thermometer in water of a few minutes after the water is boiling to allow the thermometer to reach it's maximum temperature. This lowered boiling point amounts to 1.9 degrees F. for each 1,000 feet increase in altitude."

This table I prepared shows it:

Sea Level
212*
2,000 ft
208*
5,000 ft
203*
7,500 ft
198*
10,000 ft
192*

In most cases this won't affect your meals - if boiling water just let your water continue to boil for a minute more to reach a higher temperature. Most dehydrated foods do not need boiling water, only hot water.

True, but if the water boils at 192F and you mix 8 ounces of water with 3 ounces of 30F dry food then it's only 148F. Many dishes do fine, but some don't.

I cook with a backpacking wood stove. I find that once I've brought my pot to a boil, the embers will keep things simmering for ten minutes give or take.

So I don't use a cozy. I dump whatever is being rehydrated into the boiling water and let it simmer. It's always piping hot regardless of the ambient temperature.

It occurs to me that you don't want to mess up your pot. No problem. Start with a little extra water (about 3/8 inch) in your pot. Once you add the water to your freezer bag. Put it back in the pot (with the 3/8 in. water in the bottom) and let it simmer over the embers. Depending on your pot, you may have to do something to keep the bag from touching the walls (esp. the bottom of the pot).

I used to use a spiral strip of aluminum cut from flashing to keep the bag off the bottom of the pot. Then I discovered Glad steamer bags. They don't melt. I just drop it in the water and let it simmer.

Happy FBC!

I have a steamer tray that goes in the bottom of my Jetboil pot for steaming muffins. It also works well for steaming my freezer bag back up to temp.

(Note the Jetboil doesn't apply any heat to the sides of the pot.)

I've used the FBC method during the winter in mid-twenties temperature, so as Roger pointed out it must be the cold water that was previously added. My cozy is a MYOG utilizing those slip-on beer can insulators that are made of a neoprene-like material...I just split the seam on two of them and sewed them together. Even after sitting on a cold log for ten minutes the meal is still plenty hot!